This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-368683 filed on Dec. 3, 2001.
The present invention relates to a rotary electric machine and its manufacturing method.
In an alternator disclosed in WO98/54823, a stator has a stator coil that is constructed of a plurality of U-shaped conductor segments. The segments are inserted into slots of a stator core from an axial end of the stator core and the ends of the segments are connected on the opposite axial end of the stator core. With this stator, a compact, efficient, and low cost alternator is provided.
Further, in an alternator disclosed in JP-A-2000-37132, an insulation gap between legs of U-shaped conductor segment in a turn portion is larger than that of the insert portions of the U-shaped segment, which is located in the slot, in order to improve insulation in the turn portion.
As the U-shaped segment of the stator coil, a segment 500 having its original shape shown in FIG. 10 is used. A turn portion 502 has a small curve portion 504, which is arranged adjacent to an outer diameter of the stator core in the slot, and a large curve portion 506, which is arranged adjacent to an inner diameter of the stator core in the slot. When the segments 500 are installed in the slots, the inside diameter of the coil end is smaller than the outside diameter of a rotor, thereby improving insulation in the turn portion.
In this stator, however, unevenness of the inner periphery of the coil end increases. Also, the coil end is placed close to a cooling air generating member. As a result, air pressure fluctuations increase due to gaps between the magnetic poles of the rotor and noise of a fan increases. In addition, since the inside diameter of the coil end is smaller than the outside diameter of the rotor, the flexibility of the manufacturing process planning is limited. As a result, it is difficult to reduce manufacturing costs.
Furthermore, since the coil end is close to the magnetic poles of the rotor, the magnetic field generated in the poles is likely to affect the stator coil, resulting in degradation of the performance. The above problems may occur even in the cases using segments 600 shown in FIG. 11. The segment 600 is curved in a turn portion 602 such that a curve portion 606 that is arranged adjacent to the inner diameter of the stator core is curved and a portion 604 that is arranged adjacent to the outer diameter of the stator core is substantially flat.
FIG. 9 shows a part of a stator 900 in which large segments 1331 and small segments 1332 are inserted in slots 905 of a stator core 902. An angle xcex811 formed between the longitudinal centerline of the slot 905 coincident with a radius of the stator core 902 and the centerline of the large segment 1331 is approximately 110xc2x0. An angle xcex812 formed between the longitudinal centerline of the slot 905 coincident with a radius of the stator core 902 and the centerline of the large segment 1331 is approximately 90xc2x0.
The angle xcex811 is larger than the angle xcex812. In other words, the turn portion 1331c is more curved on the inside of the stator core than the outside of the stator core. As a result, the smallest inside diameter R1 of the coil end is smaller than the inside diameter Rso of the stator core 902.
In a stator disclosed in JP-A-9-19108, multi-phase coil windings are inserted in a stator core and only the coil windings in one of the phases are curved toward an outer periphery of the stator core in a turn portion. Since only the coil windings in one of the phases are curved, the lengths of the coil windings and those of the coil windings in other phases are different. In other words, the resistances of the coil windings are different. As a result, the power generation performance decreases.
The present invention therefore has an objective to provide a rotary electric machine that is advanced in size, power output, and cost, while power generation performance, low fan noise, and ease of production are maintained.
The present invention has another objective to provide a manufacturing method for manufacturing the rotary electric machine.
A rotary electric machine of the present invention includes a rotor, a stator located radially outside the rotor, and a housing enclosing the rotor and the stator. The stator includes a stator core with a plurality of slots in its inner periphery, and a stator coil passing through the slots. The stator coil has insert portions located in the slots and connecting portions connecting the insert portions axially outside of the stator core. Each of the connecting portions has a first curve portion and a second curve portion. The first curve portion is located adjacent to an outer diameter of the stator core and the second curve portion is located adjacent to an inside diameter of the stator core. The first curve portion has curvature larger than that of the second curve portion.
With this configuration, evenness of an inner periphery of a coil end formed by the connecting portions is improved. Also, spaces between the coil end and a cooling air generating member, such as a fan, can be increased. Therefore, noise caused by the cooling air generating member is reduced. Further, since the first and second curve portions are formed on all connecting portions, resistances of conductors forming the stator coil are substantially equal. Therefore, the power generation performance can be maintained.
The stator coil is constructed of U-shaped wires. The U-shaped wire is manufactured by cutting a longitudinal wire into a predetermined length, bending the wire into a substantially U-shape, and forming a first curve portion in a curved portion of the U-shape. The first curve portion is formed on a side which is arranged adjacent to the outer diameter of the stator core. Then, the U-shape wire is twisted in a predetermined shape prior to an installation in the slot.
Since the first curve portion is formed prior to the twist and installation in the slot, the manufacturing process of the rotary electric machine is simplified. Further, manufacturing costs of the same can be reduced.